We intend to analyze non-histone proteins (NHCP) from parental and variant mouse plasma cytoma cell lines by high-resolution two-dimensional gel electrophoresis. Certain NHCP are believed to play a role in the specific regulation of gene expression and possibly in neoplastic transformation. Our variant plasmacytoma lines differ from the parental lines in their ability to synthesize heavy and light immunoglobulin polypeptide chains; we will examine these lines for qualitative or quantitative changes in NHCP which may be correlated with heavy or light chain synthesis. A second objective of our work is to investigate the expression of immunogl bulin genes in hybridomas of plasmacytoma and antibody-forming cells. Cell fusion is known to alter gene expression in certain cell lines, and we intend to see how this process may affect immunoglobulin synthesis.